The lead investigator in the Russell Williams case told CTV Ottawa in an exclusive interview Wednesday that police are not finished investigating the former colonel because they believe there could be more victims.

"The investigation into Russell Williams is still ongoing. The books are not closed on him; we are looking at him for other offences," Det.-Insp. Chris Nicholas told CTV Ottawa in the last interview he plans to give on the case, unless new charges are laid.

"Russell Williams was a person who was around the world, doing very bizarre things. It's quite uncommon . . . We're not done with him yet."

Nicholas said police find it hard to believe Williams' aggressive behaviour is limited to the crimes he pleaded guilty to this year. But while the investigation continues, police have decided not to give any more interviews to allow time for the victims' families to heal.

"We did do a good job in letting the nation know just how evil Russell Williams was; the evil things that he did. Now, it's time to heal," Nicholas said in the exclusive interview.

  • Watch Catherine Lathem's exclusive story about the police investigation

Nicholas also told CTV Ottawa a female police officer knocked on the door of Lloyd's Belleville-area home on Jan. 28, hours before she was raped, abducted and later murdered.

The officer noticed an SUV parked in a field near Lloyd's home, and drove up to her house to investigate. When the officer knocked on the door, nobody answered.

Williams was apparently hiding in the backyard at the time and broke into Lloyd's home after the officer left. Lloyd was not home yet.

Although the female officer feels sick about how the events played out, Nicholas said she should not question her actions.

"We're very proud of the officer, her observations. Obviously, she didn't know then what she knows now," Nicholas said on Wednesday.

"(The officer) did think that something could be suspicious about (the vehicle); she did attend the residence of Jessica Lloyd; she did knock on the door; she did find out that the house was secure; she did look around to see if there was anybody out there -- she didn't see anybody."

Nicholas noted that an abandoned vehicle in the middle of a farmer's field in eastern Ontario is not unusual, and not everyone would think to investigate.

"Her observations on that evening . . . was able to assist us in narrowing down the vehicles that we were looking for from 20 to probably three, which included Russell Williams' vehicle," Nicholas told CTV Ottawa.

Williams was called in for questioning in February after a police stop matched the treads on his tires to the ones left at Lloyd's home the night of her disappearance.

Williams was sentenced in October after pleading guilty to the murders of Lloyd and Marie-France Comeau, along with more than 80 sex crimes. He was sentenced to two life-terms in jail with no chance of parole for 25 years.

With a report from CTV Ottawa's Catherine Lathem